Efficient use of adsorbents for indoor air scrubbing

ABSTRACT

Some embodiments of the disclosure correspond to, for example, a method for controlling a scrubber containing an adsorbent. The scrubber may be configured to cycle between scrubbing at least one pollutant/gas from a stream of gases with the pollutant/gas being adsorbed onto the adsorbent, and regenerating at least some of the adsorbent and thereby purging at least some of the one pollutant and/or first gas from the adsorbent via a regeneration gas flow. The method may include flowing a stream of gases through the scrubber, the scrubber including the adsorbent and adsorbing at least some of the one pollutant/gas from the stream of gases onto the adsorbent during an adsorption phase over a first time period. The method may also include purging at least a portion of the one pollutant/gas from the adsorbent during a regeneration phase over a second time period with a regeneration gas flow, and cycling therebetween.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to: U.S. Provisional Patent ApplicationNo. 61/650204, filed May 22, 2012 and entitled “Air Management Systemswith Integrated Ventilation and Scrubbing Functionality”; U.S.Provisional Patent Application No. 61/664168, filed Jun. 26, 2012 andentitled “Optimal Adsorption-Regeneration Cycle for Indoor AirScrubbing”; U.S. Provisional Patent Application No. 61/664748, filedJun. 27, 2012 and entitled “Optimal Adsorption-Regeneration Cycle forIndoor Air Scrubbing”; U.S. Provisional Patent Application No.61/704796, filed Sep. 24, 2012 and entitled “Air Management Systems”.The disclosures of the above applications are incorporated herein byreference in their entireties.

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to air managementsystems and particularly to air management systems including adsorbentbased air treatment systems.

BACKGROUND

Heating, Ventilation and Air-Conditioning (“HVAC”) systems providecirculation of indoor air in enclosed environments, including buildingsand structures of all kinds, vehicles, and vessels. The HVAC system'sprimary role is to maintain comfortable temperature and humidity, aswell as good indoor air quality. In order to maintain good air quality,the circulating air should be refreshed, either by continually replacingit with fresh air from outside the enclosed environments, or by treatingit for removal of unwanted contaminants that tend to form or buildup inthe enclosed environments. The contaminants may also be referred to aspollutants, or substances. These pollutants may include carbon dioxide(CO₂) as well as volatile organic compounds (VOCs), inorganic gases likesulfur oxides, nitrous oxides, carbon monoxide, radon and others.Particles and microorganisms also represent non-gaseous pollutants thataffect indoor air quality and should be filtered or removed. Sincereplacement of indoor air may not provide a satisfactorysolution—whether due to the thermal load it imposes on the HVAC system,or due the poor air quality of the outside air, or lack of access tooutside fresh air, indoor air may be treated by means of adsorbents toremove gas pollutants.

As adsorbents collect pollutants from the air, they gradually becomesaturated and lose their adsorptive efficiency. In order to useadsorbents for an extended service period, it is often necessary toperiodically purge them in a process known as regeneration. Regenerationmay be performed by streaming a purge gas (which may also be referred toas a regeneration gas) over and/or through the adsorbent. For example,the adsorbent may be flushed with air or some other gas that has ahigher temperature and/or lower partial pressure of pollutants, or byheating the adsorbent itself, whereby the pollutant molecules arecarried off the adsorbent surface. Thus, adsorbents are often used in anadsorption- desorption “swing cycle” where in the adsorption, orcleaning, part of the cycle, they capture certain species of gases, andcontinue to do so until the adsorbent reaches saturation. Duringdesorption, or a regeneration cycle, they release the gases which wereadsorbed until they recover their original capacity and adsorptionefficiency, at which point a new cycle can begin. The swing cycle can beat least one of, for example, a temperature-swing cycle, pressure-swingcycle, or a concentration-swing adsorption cycle. In some cases bothtemperature and concentration, or temperature and pressure, may bechanged during regeneration.

The use of regenerable adsorbents for removing carbon dioxide (CO₂) andVOCs in indoor air, relying on a swing cycle is an important alternativeto air replacement, especially when the outside conditions make airreplacement energetically costly, environmentally undesirable orotherwise impractical. However regeneration economics and performanceare critical, as regeneration represents downtime for the air treatmentfunction and energy must be consumed to flow the purge gas and releasethe pollutants. Finding the optimal economic and functional performanceis further complicated by varying conditions of pollutant species andconcentration levels, as well as temperature and flow rates.

SUMMARY OF DISCLOSURE

In some embodiments of the present disclosure systems and methods aredescribed for removal of CO₂ and other pollutants from indoor air usingadsorbents and a temperature- or concentration-swing adsorption cycle.

In some embodiments of the present disclosure reversing the direction offlow during regeneration can provide advantages when one type ofpollutant is present and when more than one type of pollutant ispresent.

In accordance with some embodiments there is provided a method forreducing the level of at least one pollutant contained in indoor airfrom a human-occupied, enclosed environment. The method may compriseproviding an air treatment assembly including at least one type ofadsorbent, the adsorbent may be configured for capturing at least onepollutant entrained in an indoor air flow from the enclosed environmentand regenerating upon exposure to a regenerating gas flow; streaming theindoor air flow over and/or through the adsorbent in a first directionsuch that the adsorbent captures at least some of the pollutant from theindoor air flow, where after being flowed over and/or through theadsorbent, the air flow comprises a scrubbed air flow; and streaming theregeneration gas flow over and/or through the adsorbent in a seconddirection opposite to the first direction, such that the regenerationgas flow regenerates at least some of the adsorbent and purges at leastsome of the pollutant from the adsorbent.

In accordance with some embodiments the air treatment assembly comprisesat least two adsorbents such that the streaming indoor air flows througha first adsorbent and subsequently through a second adsorbent, and thatas a result of the reversal of the flow direction during regeneration,substances purged from the first adsorbent do not flow across the secondadsorbent.

In accordance with some embodiments, pollutants may be released from theone adsorbent during regeneration and may accumulate in the airtreatment assembly or air conduits attached to it, and as a result ofthe reversal of the flow direction during regeneration, the releasedpollutants are substantially prevented from accumulating downstream fromthe adsorbent and accumulate substantially in sections of the airtreatment assembly that are upstream from the adsorbent, the airtreatment assembly may comprise an inlet for indoor air flowing throughthe adsorbent and upstream the adsorbent being in greater proximity tothe inlet than downstream the adsorbent.

In accordance with some embodiments the pollutant and/or first gas maybe selected from the group consisting of: carbon dioxide, volatileorganic compounds, sulfur oxides, radon, nitrous oxides and carbonmonoxide. The adsorbent may comprise at least one of an amine supportedby a solid, activated carbon, clay, carbon fibers, silica, alumina,zeolites, molecular sieves, titanium oxide, polymer, porous polymers,polymer fibers and metal organic framework. The supporting solid may beat least one of silica, carbon, clay or metal oxide. The adsorbent maycomprise granular solids or pelleted shaped solids.

In accordance with some embodiments there is provided a computerimplemented method for reducing the level of at least one pollutantcontained in indoor air from an enclosed, human-occupied environment.The method may comprise streaming an indoor air flow over and/or throughan adsorbent provided within an air treatment assembly in a firstdirection, the indoor air flow containing at least one pollutant frominside the enclosed environment, such that the adsorbent captures atleast some of the pollutant from the indoor air, where after beingflowed over and/or through the adsorbent, the air flow comprises ascrubbed air flow, determining a level of an adsorption efficiency,where the adsorption efficiency at any point in time during the onecycle has a value of 1−C_(in)/C_(out), where C_(in) is the concentrationof the pollutant in the incoming air flow and C_(out) is theconcentration of the pollutant in an outgoing air flow, and where aninitial adsorption efficiency value is the adsorption efficiency valueat the beginning of the adsorption phase, where the adsorptionefficiency value is less than the initial adsorption efficiency value,streaming a regeneration air flow through the air treatment assembly andover and/or through the adsorbent in a second direction opposite to thefirst direction, such that the regeneration air flow regenerates atleast some of the adsorbent and purges at least some of the at least onepollutant from the adsorbent, where at least one of the above isperformed by a processor.

In accordance with some embodiments there is provided a system forreducing the level of at least one pollutant contained in indoor airfrom an enclosed, human-occupied environment. The method may comprise anair treatment assembly including an adsorbent, the adsorbent may beconfigured for capturing at least one pollutant entrained in an indoorair flow and regenerating upon exposure to a regenerating gas flow; andstreaming means for streaming the indoor air flow over and/or throughthe adsorbent in a first direction, such that the adsorbent captures atleast some of the at least one pollutant from the indoor air flow, andstreaming the regeneration air flow over and/or through the adsorbent ina second direction opposite to the first direction, such that theregeneration gas flow regenerates at least some of the adsorbent andpurges at least some of the pollutant from the adsorbent.

In accordance with some embodiments there is provided a system forreducing the level of at least one pollutant contained in indoor airfrom an enclosed, human-occupied environment. The system may comprise anair treatment assembly including an adsorbent, the adsorbent configuredfor capturing at least one pollutant entrained in an indoor air flow andregenerating upon exposure to a regenerating gas flow, streaming meansfor streaming the indoor air flow over and/or through the adsorbent in afirst direction, and/or for streaming the regeneration gas flow overand/or through the adsorbent in a second direction opposite to the firstdirection; at least one processor; a non-transitory machine-readablemedium storing instructions that, when executed by the processor,perform the method, which may comprise: streaming the indoor air overand/or through the adsorbent in the first direction such that theadsorbent captures at least some of the pollutant from the indoor air;and determining a level of an adsorption efficiency, where theadsorption efficiency at any point in time during the one cycle has avalue of 1−C_(in)/C_(out), where C_(in) is the concentration of thepollutant in the incoming air flow and C_(out) is the concentration ofthe pollutant in an outgoing air flow, and where an initial adsorptionefficiency value is the adsorption efficiency value at the beginning ofthe adsorption phase, where the adsorption efficiency value is less thanthe initial adsorption efficiency value, streaming of the regenerationgas flow over and/or through the adsorbent is performed.

In some embodiments, a method for controlling a scrubber containing anadsorbent, the scrubber configured to cycle between scrubbing at leastone pollutant and/or first gas from a stream of gases with the at leastone pollutant and/or first gas being adsorbed onto the adsorbent, andregenerating at least some of the adsorbent and thereby purging at leastsome of the at least one pollutant and/or first gas from the adsorbentvia a regeneration gas flow. The method may comprise flowing a stream ofgases through the scrubber, the scrubber comprising the adsorbent,adsorbing at least some of the one pollutant and/or first gas from thestream of gases onto the adsorbent during an adsorption phase over afirst time period, purging a portion of the at least one pollutantand/or first gas from the adsorbent during a regeneration phase over asecond time period with a regeneration gas flow, and cycling between theadsorption phase and the regeneration phase. The method may also includelimiting at least one of: the duration of the first time period to aperiod of time which is less than the time required to have theadsorbent adsorb as much of the pollutant/gas as the adsorbent canadsorb complete adsorption phase, and the duration of the second timeperiod to a period of time which is less than the time required tocompletely regenerate the adsorbent.

In accordance with some embodiments there is provided a method forreducing the level of at least one pollutant contained in indoor airfrom an enclosed, human-occupied environment. The method may compriseproviding an air treatment assembly including an adsorbent, theadsorbent configured for capturing at least one pollutant entrained inan indoor air flow from the enclosed environment and regenerating uponexposure to a regenerating gas flow streaming the indoor air flow overand/or through the adsorbent in a first direction such that theadsorbent captures at least some of the at least one pollutant from theindoor air flow, where the streaming of the indoor air flow over and/orthrough the adsorbent comprises an adsorption phase; and streaming theregeneration gas flow over and/or through the adsorbent in a seconddirection opposite to the first direction, such that the regenerationair flow regenerates at least some of the adsorbent and purges at leastsome of the at least one pollutant from the adsorbent, where thestreaming of the regeneration gas flow over and/or through the adsorbentcomprises a regeneration phase, cycling between the adsorption phase andthe regeneration phase, where one cycle comprises an adsorption phasefollowed by a regeneration phase, one cycle period comprises the totaltime elapsed during one cycle; the at least one pollutant purged fromthe adsorbent is carried away by the regeneration gas flow, and acomplete regeneration phase comprises a time period for removingsubstantially all of the at least one pollutant from the adsorbentduring the regeneration phase, and a complete adsorption phase comprisesa time period for substantially saturating all the adsorbent during theadsorption; and limiting at least one of: the duration of the first timeperiod to a period of time which is less than the complete adsorptionphase, and the duration of the second time period to a period of timewhich is less than the complete regeneration phase.

In accordance with some embodiments prior to streaming the regenerationgas flow the method may further include determining a level of anadsorption efficiency, where the adsorption efficiency at any point intime during the one cycle has a value of 1−C_(in)/C_(out), where C_(in)is the concentration of the pollutant in the incoming air flow andC_(out) is the concentration of the pollutant in an outgoing air flow,and where an initial adsorption efficiency value is the adsorptionefficiency value at the beginning of the adsorption phase, where theadsorption efficiency value is less than the initial adsorptionefficiency value, streaming of the regeneration gas flow over and/orthrough the adsorbent is performed.

In accordance with some embodiments the adsorption efficiency value isat least about 20% less than the initial adsorption efficiency value. Inaccordance with some embodiments the adsorption efficiency value is atleast about 30% less than the initial adsorption efficiency value. Inaccordance with some embodiments the adsorption efficiency value is atleast about 50% less than the initial adsorption efficiency value. Inaccordance with some embodiments the adsorption efficiency value is atleast about 80% less than the initial adsorption efficiency value.

In some embodiments of the present disclosure a key for optimal systemeconomics is to terminate the regeneration phase and the adsorptionphase before they are complete, as the rates of adsorption anddesorption decline. A detailed analysis shows how to identify and setthe optimal points at which to switch over from regeneration toadsorption and vice versa.

In accordance with some embodiments there is provided a method forcontrolling a scrubber containing an adsorbent, the scrubber may beconfigured to cycle between scrubbing at least one pollutant and/orfirst gas from a stream of gases with the pollutant and/or first gasbeing adsorbed onto the adsorbent, and regenerating at least some of theadsorbent and thereby purging at least some of the pollutant and/orfirst gas from the adsorbent via a regeneration gas flow. The method mayinclude flowing a stream of gases through the scrubber, the scrubbercomprising the adsorbent; adsorbing at least some of the pollutantand/or first gas from the stream of gases onto the adsorbent during anadsorption phase over a first time period; purging a portion of thepollutant and/or first gas from the adsorbent during a regenerationphase over a second time period with a regeneration gas flow, andcycling between the adsorption phase and the regeneration phase. Onecycle may comprise at least an adsorption phase followed by aregeneration phase, one cycle period may comprise the total time elapsedduring one cycle. The pollutant and/or first gas purged from theadsorbent may be carried away by the regeneration gas flow. A completeregeneration phase may comprise a time period for removing substantiallyall of the pollutant and/or first gas from the adsorbent during theregeneration phase, and a complete adsorption phase may comprise a timeperiod for substantially saturating all the adsorbent during theadsorption. The method may include limiting at least one of: theduration of the first time period to a period of time which is less thanthe complete adsorption phase, and/or the duration of the second timeperiod to a period of time which is less than the complete regenerationphase.

In accordance with some embodiments, the first time period may compriseabout 95% of a complete adsorption phase. In accordance with someembodiments, the first time period is about 90% of a complete adsorptionphase. In accordance with some embodiments, the first time period isabout 80% of a complete adsorption phase. In accordance with someembodiments, the first time period is about 50% of a complete adsorptionphase. In accordance with some embodiments, the first time period isabout 20% of a complete adsorption phase. In accordance with someembodiments, the first time period comprises about 20% to about 95% of acomplete adsorption phase.

In accordance with some embodiments, the second time period comprisesabout 95% of a complete regeneration phase. In accordance with someembodiments, the second time period is about 90% of a completeregeneration phase. In accordance with some embodiments, the second timeperiod is about 80% of a complete regeneration phase. In accordance withsome embodiments, the second time period is about 50% of a completeregeneration phase. In accordance with some embodiments, the second timeperiod is about 20% of a complete regeneration phase. In accordance withsome embodiments, the second time period comprises about 20% to about95% of a complete regeneration phase.

In accordance with some embodiments, the regeneration phase may beterminated upon a regeneration rate R(t_(r)) of the adsorbent beingbetween about equal to and a predetermined amount less than aproductivity p of the complete regeneration phase, where productivityp=C/T, and C equals an amount of the pollutant and/or first gas adsorbedby the adsorbent from the stream of gases during one cycle and T is theduration of one cycle period.

In accordance with some embodiments, the regeneration phase isterminated upon a regeneration rate R(t_(r)) being between about equalto and about twice a productivity p of the complete regeneration phase,where productivity p=C/T, and C equals an amount of the pollutant and/orfirst gas adsorbed by the adsorbent from the stream of gases during onecycle and T is the duration of one cycle period.

In accordance with some embodiments, the pollutant and/or first gas maybe selected from the group consisting of: carbon dioxide, volatileorganic compounds, sulfur oxides, radon, nitrous oxides and carbonmonoxide. The adsorbent may comprise at least one of: an amine supportedby a solid, activated carbon, clay, carbon fibers, silica, alumina,zeolites, molecular sieves, titanium oxide, polymer, porous polymers,polymer fibers and metal organic frameworks. The supporting solid may beat least one of silica, carbon, clay or metal oxide. The adsorbent maycomprise granular solids or pelleted shaped solids. The stream of gasesmay comprise air from an enclosed environment, outdoor air, flue gases,or nitrogen with elevated levels of carbon dioxide or organiccontaminants, relative to substantially unpolluted air.

In accordance with some embodiments, the one cycle may further compriseat least one of: (i) a first switchover phase prior to the regenerationphase, and (ii) a second switchover phase following the regenerationphase. The second switchover phase may comprise a period of time tobring the adsorbent to a temperature to adsorb pollutant and/or firstgas during the adsorption phase. The first switchover phase may comprisea period of time to bring the adsorbent to a temperature to release theat least one pollutant and/or first gas from the adsorbent during theregeneration phase.

In accordance with some embodiments, prior to streaming the regenerationgas flow the method may further include determining a level of anadsorption efficiency, where the adsorption efficiency at any point intime during the one cycle has a value of 1−C_(in)/C_(out), where C_(in)is the concentration of the pollutant in the incoming air flow andC_(out) is the concentration of the pollutant in an outgoing air flow,and where an initial adsorption efficiency value is the adsorptionefficiency value at the beginning of the adsorption phase. Theadsorption efficiency value is less than the initial adsorptionefficiency value, streaming of the regeneration gas flow over and/orthrough the adsorbent is performed.

In accordance with some embodiments there is provided a system forcontrolling a scrubber, the system may comprise a scrubber containing anadsorbent, the scrubber may be configured to cycle between scrubbing atleast one pollutant and/or first gas from a stream of gases with the atleast one pollutant and/or first gas being adsorbed onto the adsorbent,and purging the at least one pollutant and/or first gas from theadsorbent via a regeneration gas flow; means for flowing the stream ofgases through the scrubber and over and/or through the adsorbent, wherethe adsorbent adsorbs at least one pollutant and/or first gas from thestream of gases during an adsorption phase over a first time period;means for flowing the regeneration gas flow over the adsorbent forpurging a portion of the pollutant and/or first gas from the adsorbentduring a regeneration phase over a second time period with aregeneration gas flow, and means for cycling between the adsorptionphase and the regeneration phase. One cycle may comprise one adsorptionphase followed by one regeneration phase. One cycle period may comprisethe total time elapsed during one cycle. The pollutant and/or first gaspurged from the adsorbent may be carried away by the regeneration gasflow. A complete regeneration phase may comprise a time period forremoving substantially all of the pollutant and/or first gas from theadsorbent during the regeneration phase. A complete adsorption phasecomprises a time period for substantially saturating all the adsorbentduring the adsorption. The duration of at least one of the following maybe limited: the duration of the first time period to a period of timewhich is less than the complete adsorption phase, and the duration ofthe second time period to a period of time which is less than thecomplete regeneration phase.

In accordance with some embodiments, the means for cycling may comprisea processor and a non-transitory machine-readable medium storinginstructions (for example), having computer instructions/code operatingthereon for controlling cycling between the adsorption and regenerationphases.

In accordance with some embodiments there is provided a computerimplemented method for controlling a scrubber containing an adsorbent,the scrubber may be configured to cycle between scrubbing at least onepollutant and/or first gas from a stream of gases with the at least onepollutant and/or first gas being adsorbed onto the adsorbent, andpurging the at least one pollutant and/or first gas from the adsorbentvia a purging gas flow, the method comprising: flowing a stream of gasesthrough the scrubber, the scrubber including or comprising an adsorbent;adsorbing at least one pollutant and/or first gas from the stream ofgases onto the adsorbent during an adsorption phase over a first timeperiod, purging a portion of the at least one pollutant and/or first gasfrom the adsorbent during a regeneration phase over a second time periodwith a regeneration gas flow, and cycling between the adsorption phaseand the regeneration phase. One cycle may comprise one adsorption phasefollowed by one regeneration phase. One cycle period may comprise thetotal time elapsed during one cycle. At least one pollutant and/or firstgas purged from the adsorbent may be carried away by the regenerationgas flow. A complete regeneration phase comprises a time period forremoving substantially all of the pollutant and/or first gas from theadsorbent during the regeneration phase. A complete adsorption phase maycomprise a time period for substantially saturating all the adsorbentduring the adsorption. The method may include limiting at least one of:the duration of the first time period to a period of time which is lessthan the complete adsorption phase, and the duration of the second timeperiod to a period of time which is less than the complete regenerationphase, where at least one of the above is performed by at least oneprocessor.

In accordance with some embodiments there is provided a system forcontrolling a scrubber containing an adsorbent, the scrubber may beconfigured to cycle between scrubbing at least one pollutant and/orfirst gas from a stream of gases with the pollutant and/or first gasbeing adsorbed onto the adsorbent, and purging the pollutant and/orfirst gas from the adsorbent via a regeneration gas flow. The system maycomprise at least one processor and a non-transitory machine-readablemedium storing instructions that, when executed by the at least oneprocessor, perform the method which may comprise: flowing a stream ofgases over and/or through the adsorbent, where the adsorbent adsorbs atleast some of the pollutant and/or first gas from the stream of gasesduring an adsorption phase over a first time period; purging a portionof the pollutant and/or first gas from the adsorbent during aregeneration phase over a second time period with a regeneration gasflow, and cycling between the adsorption phase and the regenerationphase. One cycle may comprise one adsorption phase followed by oneregeneration phase. One cycle period may comprise the total time elapsedduring one cycle. At least one pollutant and/or first gas purged fromthe adsorbent may be carried away by the regeneration gas flow. Acomplete regeneration phase comprises a time period for removingsubstantially all of the pollutant and/or first gas from the adsorbentduring the regeneration phase. A complete adsorption phase may comprisea time period for substantially saturating all the adsorbent during theadsorption. The method may include limiting at least one of: theduration of the first time period to a period of time which is less thanthe complete adsorption phase, and the duration of the second timeperiod to a period of time which is less than the complete regenerationphase.

BRIEF DESCRIPTION OF THE DRAWINGS

The principles and operations of the systems, apparatuses and methodsaccording to some embodiments of the present disclosure may be betterunderstood with reference to the drawings, and the followingdescription. These drawings are given for illustrative purposes only andare not meant to be limiting.

FIGS. 1A-1C are each a schematic illustration of an air managementsystem according to some embodiments of the present disclosure;

FIGS. 2A and 2B are each a schematic illustration of an air managementsystem according to some embodiments of the present disclosure;

FIG. 3 is a schematic illustration of an air treatment assemblyaccording to some embodiments of the present disclosure; and

FIG. 4 is a graph showing an adsorption-regeneration cycle according tosome embodiments of the present disclosure.

DETAILED DESCRIPTION

Removing carbon dioxide (CO₂) and volatile organic compounds (VOCs) fromindoor air, or reducing the level of at least one pollutant or a gascontained in indoor air from an enclosed environment, can pave the wayfor improved indoor air quality and lower energy costs in enclosedenvironments. In some embodiments, adsorbents, such as solid adsorbents,are used to scrub unwanted pollutants including gases and vapors, fromindoor air, namely pollutants entrained in an indoor air flow from theenclosed environment. Adsorbents selective to CO₂ are known in the artand include, but are not limited to, various types of amines andsolid-supported amines, as well as clays, molecular sieves, zeolites,various forms of silica and alumina, various forms of carbon, activatedcarbon, carbon fibers, titanium oxide, porous polymers, polymer fibersand metal organic frameworks.

Adsorbents selective to VOCs may include molecular sieves, activatedcarbon, zeolites, carbon fibers and carbon particles, for example. Insome embodiments more than one type of adsorbent is used.

In some embodiment there may be a first layer or bed of an adsorbent forcapturing CO₂, and a second layer of an adsorbent for capturing VOCs,positioned downstream from the first layer, relative to the direction ofthe air flow of incoming indoor air. In some embodiments, the firstlayer may comprise solid supported amines for capturing CO₂, and thesecond layer may comprise carbon adsorbents for capturing VOCs.

FIGS. 1A-1C are each a schematic illustration of an air managementsystem 100 including a scrubber, which may be referred to as an airtreatment assembly 102. The air management system 100 may include an aircirculation system, such as a central HVAC system 108 provided to manageand circulate indoor air within an enclosed environment 110.

The enclosed environment 110 may comprise an office building, acommercial building, a bank, a residential building, a house, a school,a factory, a hospital, a store, a mall, an indoor entertainment venue, astorage facility, a laboratory, a vehicle, an aircraft, a ship, a bus, atheatre, a partially and/or fully enclosed arena, an education facility,a library and/or other partially and/or fully enclosed structure and/orfacility which can be at times occupied by equipment, materials, liveoccupants (e.g., humans, animals, synthetic organisms, etc.) and/or anycombination thereof.

The HVAC system 108 shown in FIGS. 1A-1C may comprise an air handlingunit 114 in fluid communication with the enclosed environment 110. Theair handling unit 114 may provide air circulation to various parts ofthe enclosed environment 110 by means of ducts 116 or conduits, as shownin FIGS. 1A-1C. The air handling unit 114 may include any suitableconfiguration for conditioning the temperature and humidity of the airflowing through it. Conditioned air exiting the air handling unit 114may be provided to the enclosed environment 110 as supply air 118.Return air 120, which is indoor air 120 from the enclosed environment110, may exit the enclosed environment 110 via ducts 122 or a plenum orany other suitable means.

In some embodiments, a portion of the return air 120 may be exhausted asexhaust air 124, directly or via ducts 126. Outside, fresh air 130 maybe introduced into the air handling unit 114 via ducts 132.

The air treatment assembly 102 may be placed in any suitable locationwithin the enclosed environment relative to the air management system100 and is configured to receive at least a portion of the indoor air.In some embodiments, as shown in FIG. 1A, the air treatment assembly 102is placed in parallel to the air handling unit 114. A portion of thereturn air 120 may flow to the air treatment assembly 102 and thereafterto the air handling unit 114 and the remaining portion may flow directlyto the air handling unit 114 and/or may be exhausted as exhaust air 124,via ducts 126.

In some embodiments, as shown in FIG. 1B, the air treatment assembly 102is placed in series with the air handling unit 114, either upstreamrelative to the air handling unit 114 or downstream thereof. A portionof the return air 120 may flow to the air treatment assembly 102 andthereafter to the air handling unit 114 and a portion may be exhaustedas exhaust air 124, via ducts 126.

In some embodiments, as shown in FIG. 1C, the air treatment assembly 102is not in direct fluid communication with the air handling unit 114, andmay be placed within the enclosed environment 110. A portion ofcirculating indoor air 120 may flow into the air treatment assembly 102and thereout, back into the enclosed environment 110.

FIGS. 2A and 2B are each a schematic illustration of an air managementsystem 200 comprising the air treatment assembly 102. The air managementsystem 200 may include a distributed air circulation system 208comprising one or more fan-coil units 210 provided to manage andcirculate indoor air within the enclosed environment 110.

In some embodiments, as seen in FIGS. 2A and 2B, the enclosedenvironment 110 may comprise a plurality of rooms 220. A fan-coil unit210 may be placed in one or more of the rooms 220. An air treatmentassembly 102 may be placed in one or more of the rooms 220. At least aportion of return air 120, comprising indoor air from the room 220, mayflow into the air treatment assembly 102 and a separate stream of airmay flow into the fan-coil unit 210 and/or may be exhausted out of theroom 220.

The air treatment assembly 102 may be placed at any suitable location.In some embodiments, as shown in FIG. 2A, scrubbed air flowing out ofthe air treatment assembly 102 may flow directly to the fan-coil unit210 via a duct 222.

In some embodiments, as shown in FIG. 2B, the air treatment assembly 102may not be in direct fluid communication with the fan-coil unit 210. Atleast a portion of indoor air 120 may flow into the air treatmentassembly 102 and a portion may flow into the fan-coil unit 210.

In accordance with some embodiments, as seen in FIG. 3, the airtreatment assembly 102 may be provided to reduce the concentration ofunwanted substances or pollutants present in the air introduced therein.The air treatment assembly 102 may comprise one or more adsorbent bedsor layers for one or more types of pollutants. For example, a firstadsorbent 230 may be provided for capturing gas pollutants, such as CO₂and a second adsorbent 234 may be provided for capturing other gaspollutants, such as VOCs. Examples of air treatment assemblies aredisclosed in applicant's U.S. Pat. No. 8,157,892, which is incorporatedherein by reference in its entirety.

The CO₂ adsorbent 230 may comprise a solid supported amine, such asdisclosed in applicant's PCT application PCT/U.S. Ser. No. 12/38343,which is incorporated herein by reference in its entirety.

In the example of FIG. 3, the first adsorbent 230 may be formed of anadsorbent bed comprising adsorbent particles 236. The adsorbentparticles 236 may comprise solid supported amines or any other adsorbentmaterial, in any suitable form, such as granular solids or pelletedshaped solids, for example. The second adsorbent 234 may be formed of alayer 238 comprising a carbon cloth or any other suitable material.

During scrubbing, the air treatment assembly 102 may operate in a cyclecomprising an adsorption phase and a regeneration phase. In theadsorption phase the pollutants, such as the CO₂ or VOCs, are firstcaptured and adsorbed by the adsorbents, which as described above, maycomprise one or more adsorbents, such as adsorbents 230 and 234.Following the capture of these pollutants in the adsorption phase, theadsorbent may be regenerated during the regeneration phase by urging therelease of the pollutants therefrom.

The regeneration may be performed in any suitable manner. For example,regeneration may be performed by exposing, (e.g. by flushing) theadsorbent to a purge gas for purging and releasing at least a portion ofthe pollutants therefrom.

In some embodiments, the purge gas may comprise outdoor air 240. Theoutdoor air 240 may be heated prior to entering the air treatmentassembly 102 by any suitable method, such as will be further described.

Incoming contaminated indoor air 120 from the enclosed environment 110is shown in FIGS. 1A-3 as flowing in a first direction into the airtreatment assembly 102 through an aperture or a first inlet 244, whichmay be controlled by an inlet damper 248 or any other suitable means.Scrubbed air may exit the air treatment assembly 102 via an oppositelyfacing aperture or second outlet 250, which may be controlled by anoutlet damper 254 or any other suitable means. The incoming side isreferred to as upstream and the outgoing side as downstream.

During the regeneration phase the outdoor air 240, shown as a dashedline, may flow into the air treatment assembly 102 via an inlet 260,which may be controlled by an inlet damper 264. The outside air 240 mayflow out of the air treatment assembly 102 via an outlet 268, which maybe controlled by an outlet damper 270. The inlet damper 264 and outletdamper 270 may be open during the regeneration phase while the inletdamper 248 and outlet damper 254 are generally closed.

During the adsorption phase the inlet damper 264 and outlet damper 270may be closed while the inlet damper 248 and outlet damper 250 aregenerally open.

In some embodiments, the outdoor air 240 may flow into a heatingsubassembly 280 for heating the outdoor air 240 therein before enteringthe air treatment assembly 102. Heating the outdoor air 240 may beperformed in any suitable manner, such as by an electrical heating coilplaced within the heating subassembly 280. Additional methods forheating the outdoor air 240 include: water coils using hot waterprovided from a separate source; direct or indirect solar heat; afurnace using gas or other fuel; a heat pump; or any other suitablesource of heat. The outdoor air 240 may be heated from the ambienttemperature to any suitable temperature, typically within a range ofapproximately 30-120° C. Alternatively, the outdoor air 240 may beheated to a temperature less than 80° C. Alternatively, the outdoor air240 may be heated to a temperature less than 50° C. Alternatively, theoutdoor air 240 may enter the air treatment assembly 102 at the ambienttemperature without prior heating thereof.

It is noted that the heating subassembly 280 may be placed in anysuitable location. For example, the heating subassembly 280 may beplaced in proximity to the air treatment assembly 102 or may be locatedat a certain distance whereby warm, outdoor air 240 may be deliveredfrom the heating subassembly 280 to the air treatment assembly 102 via aconduit (not shown).

In accordance with an embodiment, as shown in FIGS. 1A-3, the outdoorair 240, during the regeneration phase may flow in a second direction,which is the opposite direction of the indoor air flow during theadsorption phase (i.e. the first direction).

In order to enable the reverse direction of the air flow duringregeneration, the air treatment assembly 102 may be configured with anappropriate fan 290 or fans that either pushes the outside air 240 intothe air treatment assembly 102 near the inlet 260 or pulls the outsideair 240 thereout at outlet 268, as shown in FIGS. 1A-3. The fan 290 canbe part of the air treatment assembly 102 or can be incorporated intothe air heating subassembly 280 or any other suitable location withinthe air management system 100 of FIG. 1A-1C or air management system 200of FIGS. 2A and 2B.

The air treatment assembly 102 may comprise additional fans, such as fan292, for pushing or pulling the return air 120 through the air treatmentassembly 102.

In other embodiments the direction of air flow in regeneration is in thesame direction of the return air flow.

The reverse air flow during the regeneration phase offers certainadvantages which are best understood in relation to FIG. 3 and insertsthereof. During adsorption, pollutant laden air first encounters anupstream section or surface 300 of the adsorbent bed and the air isgradually depleted of CO₂ or other pollutants as it advanced through thebed, away from surface 300. The adsorbent material near this surface 300receives the most contaminated air and as a result, there is typically ahigher load of captured pollutants 304 in the upstream side of theadsorbent bed, than in an oppositely facing surface 308 in thedownstream side of the adsorbent bed. During regeneration, if the flowis in the same direction of the return air flow, the pollutants carriedfrom the upstream side are forced to flow through the entire bed ontheir way out, and through subsequent adsorbent layers (such as layer238) if there are such. This may increase the likelihood that some ofthese purged pollutants will be recaptured. If the flow is reversed, thehighest concentration of pollutants is removed backwards and away fromthe upstream section without passing through the bed. A similar dynamicmay apply also to captured dust particles 310.

The considerations is also significant when a dual adsorbent system isdeployed, such as with the second adsorbent 234, e.g. the VOC adsorbentlayer 238, downstream from the first adsorbent 230, such as the CO₂adsorbent. This is because the CO₂ adsorbent may release VOCs andparticles or vapors 314 during regeneration. For example, a solidsupported amine based CO₂ adsorbent may release some amine vapors 314during high temperature regeneration. These vapors 314 are preferablyexhausted directly and not forced to flow through the VOC adsorbentwhere they may be captured, thus loading and contaminating the VOCadsorbent 234 instead of allowing it to be purged and regenerated. Byreversing the flow direction in regeneration, clean air passes thoughthe VOC adsorbent 234 first and then through the CO2 adsorbent 230, sothat any volatilized amines are carried away from the VOC adsorbent 234rather than through it.

Furthermore, granular adsorbents 236 may release their own dustparticles 310 and it is preferable to exhaust them without passing themthrough the air treatment assembly 102 downstream dust filter 320 or afiber cloth, such as layer 238, where dust particles 310 can buildup andimpede air flow.

The reverse air flow during the regeneration phase may be significant inany air treatment assembly including or comprising a single or pluralityof adsorbents configured to adsorb any pollutants from incoming air.

In some embodiments, pollutants may be released from the adsorbentduring regeneration and may accumulate in the air treatment assembly 102or air conduits attached to it or sections of the air treatment assembly102. As a result of the reversal of the flow direction duringregeneration the released pollutants may be substantially prevented fromaccumulating downstream from the adsorbent and accumulate substantiallyin sections of the air treatment assembly that are upstream from theadsorbent. Upstream the adsorbent may also be defined as being ingreater proximity to the inlet 244 than downstream the adsorbent.

It is noted in reference to FIGS. 1A-3, that any other suitable meansbesides dampers, such as valves, fans or shutters, may be used tocontrol the volume of air entering and/or exiting the air treatmentassembly 102 or flowing the incoming air (or stream of gases) throughthe air treatment assembly 102. Additionally, blowers or any othersuitable means for urging flow of air may be used in place of or inaddition to the fans of the air treatment assembly 102.

It is further noted in reference to FIGS. 1A-3, that any suitablestreaming means may be provided, such as dampers, fans, (such as shownin FIG. 3), valves, and/or shutters and ducts inlets and outlets (suchas shown in FIGS. 1A-3) and/or conduits. The streaming means may be usedfor streaming the indoor air flow over and/or through the adsorbent inthe first direction, such that the adsorbent captures at least thepollutant or first gas from the indoor air flow. The streaming means mayfurther be used for streaming the regeneration air flow over and/orthrough the adsorbent in the second direction opposite to the firstdirection, such that the regeneration gas flow regenerates at least someof the adsorbent and purges at least some of the pollutant from theadsorbent.

In some embodiments, the air management system 100 of FIG. 1A-1C or airmanagement system 200 of FIGS. 2A and 2B may include fans, and dampersor any other suitable means for circulating air therein.

Optimizing the Cycle Length and Regeneration Time

Due to the need to treat large volumes of air for extended periods oftime with a finite amount of adsorbent, it is advantageous to generallycontinually reuse the same adsorbent by means of a temperature swingcycle or a concentration swing cycle or some combination thereof. Theproblem is particularly important in the case of CO₂ due to its largecumulative volumes, but in principle carries over to most other gasesand vapors. Generally that means that the adsorbent undergoes a cyclewith several phases in each cycle. In the adsorption phase, theadsorbent selectively captures and removes certain gases from the airflow, and in the regeneration phase it releases the captured gases,presumably to a purge gas that is exhausted. During regeneration one orboth of the following conditions may be met, (a) the adsorbent is warmerthan it was during adsorption and/or (b) the incoming purge gas haslower partial pressure of the released pollutants.

As the adsorption phase progresses, the adsorbent gradually becomessaturated with CO₂ (or other pollutants) and its ability to adsorbbegins to degrade, eventually stopping adsorption entirely. Thetransition can be gradual or fairly sharp, depending on a number ofparameters including the flow rate, temperature, thickness of adsorbentbed, and of course the chemistry and structural properties of theadsorbent.

During the regeneration phase the adsorbent is purged. The amount ofadsorbed gas that is released is initially high and then graduallydeclines as the adsorbent is depleted from the captured gas. As theamount of gas released tapers off, a substantial fraction of theregeneration time is spent on extracting a small residual fraction ofthe amount of pollutants.

In some embodiments there may be continual scrubbing of the indoor airas it circulates. The time spent regenerating the adsorbent is time whenthe adsorbent is “off line” and not being utilized. This time spentregenerating may be kept as short as possible.

In accordance with some embodiments of the present disclosure, there isan adsorption-regeneration cycle that is incomplete, limited orinterrupted by design. The phases are switched from adsorption toregeneration before the adsorbent is saturated, and the regenerationprocess may be stopped well before all the pollutants are released. Thisis done in order to achieve the best economics for indoor air scrubbing.

In some embodiments, the air treatment assembly 102 or scrubber may beconfigured to cycle between scrubbing at least one pollutant and/or gasfrom the stream of gases with the pollutant, and regenerating at leastsome of the adsorbent. The adsorption-regeneration cycle may comprise anadsorption phase which may be followed by a regeneration phase.

A complete adsorption phase may comprise a first time period forsubstantially saturating the adsorbent during the adsorption phase underthe adsorption flow and temperature conditions being used. Similarly, acomplete regeneration phase may comprise a second time period forremoving substantially all of the removable pollutants and/or first gasfrom the adsorbent during the regeneration phase, under the purge flowand temperature conditions being used.

In accordance with some embodiments of the present disclosure, theduration of the second time period may be limited to a period of timewhich is less than the complete regeneration phase. Additionally oralternatively, the duration of the first time period may be limited to aperiod of time which is less than the complete adsorption phase.

In some embodiments the adsorption-regeneration cycle may comprise anadsorption phase followed by an optional first switchover time period,which may be followed by a regeneration phase. The regeneration phasemay be followed by an optional second switchover time period.

In some embodiments, during the first switchover time period theadsorbent may be heated or may be maintained at the same temperature. Insome embodiments, during the second switchover time period the adsorbentmay be cooled down. The cool down may be facilitated by flowing unheatedair through the sorbent during this time.

In accordance with some embodiments, the first switchover time periodmay comprises a period of time to bring the adsorbent to a temperatureto release the pollutant from the adsorbent during the regenerationphase. The second switchover time period may comprise a period of timeto bring the adsorbent to a temperature to adsorb the pollutant duringthe adsorption phase.

In a non-limiting example, the first time period may comprise about 95%of a complete adsorption phase. In some embodiments, the first timeperiod may comprise about 90% of a complete adsorption phase. In someembodiments, the first time period may comprise about 80% of a completeadsorption phase. In some embodiments, the first time period maycomprise about 50% of a complete adsorption phase. In some embodiments,the first time period may comprise about 20% of a complete adsorptionphase. In some embodiments, the first time period may comprise about20%-95% of a complete adsorption phase.

In a non-limiting example the second time period may comprise about 95%of a complete regeneration phase. In some embodiments, the second timeperiod may comprise about 90% of a complete regeneration phase. In someembodiments, the second time period may comprise about 80% of a completeregeneration phase. In some embodiments, the second time period maycomprise about 50% of a complete regeneration phase. In someembodiments, the second time period may comprise about 20% of a completeregeneration phase. In some embodiments, the second time period maycomprise about 20%-95% of a complete regeneration phase.

Determining the duration of the limited period of time for theregeneration phase and/or the adsorption phase may be performed in anysuitable manner, such as empirically via experimentation, for example.

In some embodiments, determining the duration of the limited period maybe performed by a computer including a processor and a non-transitorymachine-readable medium (for example).

In some embodiments, controlling cycling between the adsorption andregeneration phases may be performed by a computer including a processorand a non-transitory machine-readable medium, storing instructionshaving computer instructions operating thereon (for example).

In some embodiments, optimizing the cycle length and regeneration timemay be performed by a system for controlling the air treatment assembly102 (which may be referred to as the scrubber). The air treatmentassembly 102 containing the adsorbent may be configured to cycle betweenscrubbing the pollutant and/or gas from the stream of gases in theincoming air and/or gas being adsorbed onto the adsorbent, and purgingthe pollutant and/or first gas from the adsorbent, via the regenerationgas flow. The air treatment assembly 102 may include means for flowingthe stream of gases through the air treatment assembly 102 and overand/or through the adsorbent, where the adsorbent adsorbs the pollutantand/or gas from the stream of gases during the adsorption phase over afirst time period. The air treatment assembly 102 may include means forflowing the regeneration gas flow over the adsorbent for purging aportion of the pollutant and/or first gas from the adsorbent during aregeneration phase over a second time period with a regeneration gasflow. The air treatment assembly 102 may include means for cyclingbetween the adsorption phase and the regeneration phase, where one cyclemay comprise one adsorption phase followed by one regeneration phase.One cycle period may comprise the total time elapsed during a completecycle or summation of the first time period, and the second time period.A complete regeneration phase may comprise a time period for removingsubstantially all of the pollutant and/or gas that can be removed fromthe adsorbent during the regeneration phase. A complete adsorption phasemay comprise a time period for substantially saturating all theadsorbent during the adsorption. The duration of at least one of thefollowing may be limited: the first time period to a period of timewhich is less than the complete adsorption phase and the second timeperiod to a period of time which is less than the complete regenerationphase.

In some embodiments, the means for cycling may comprise a processor anda non-transitory machine-readable medium storing instructions havingcomputer instructions operating thereon for controlling cycling betweenthe adsorption and regeneration phases (for example).

In some embodiments, the means for cycling may comprise a control unit(not shown), such as an automated electromechanical control unit thatdetermines when to open or close the dampers shown in FIG. 3, forexample, when to activate fans of FIG. 3, for example, and may beresponsible for flowing the incoming air purge gas through the system,for example. The air management system 100 of FIGS. 1A-1C and airmanagement system 200 of FIGS. 2A-2B may also operate with sensors andactuators or any other suitable elements configured for determining whento activate the cycling means.

As described in reference to FIGS. 1A-3, the means for flowing thestream of gases through the scrubber and the means for flowing theregeneration gas flow may comprise any suitable means. For example, themeans may comprise dampers, fans, (such as shown in FIG. 3), valves,and/or shutters and ducts, inlets and outlets (such as shown in FIGS.1A-3) and/or conduits.

In accordance with some embodiments the following analysis may beperformed for determining the duration of the limited time period. Theanalysis is described in reference to a pollutant comprising CO₂, but isapplicable to any other pollutants.

A general rationale for incomplete regeneration is as follows: If therate of release of CO2 slows down to a trickle, the adsorbent is nearingits clean state and can already be put to work effectively, so just likethere is no reason to let the adsorbent idle, there is no reason tospend too much time regenerating it to the last few percent of capacity.The question is, what is the right time to stop regeneration and toswitch back to adsorption.

For a given set of regeneration conditions, the rate of release of CO₂is denoted by R(t), measured in units of mass per time (such as molesper minute, grams per second, etc.), where t denotes the time measuredfrom the beginning of the regeneration cycle. Typically R(t) increasesat the beginning of the regeneration cycle as the adsorbent is heatedwhile it is still loaded with CO₂ but soon thereafter starts decliningover time, as the amount of captured CO₂ declines during theregeneration cycle, and thus, R(t) gradually trails off over an extendedperiod.

On the adsorption side there is an analogous situation where A(t) is therate at which CO₂ is removed from the air flow, again measured in unitsof mass per time, and in analogy to R(t), it generally decreases as afunction of time.

The typical cycle would have the adsorption phase continue for a timeperiod of t_(a) and then have the regeneration phase continue for aperiod t_(r). Since the amounts of carbon adsorbed and released have tobalance each other in repeated cycles over the long run, it may be thatthe total amount adsorbed in a single adsorption phase, C, equals theamount released in a single regeneration phase, namely:

∫₀ ^(t) ^(a) A(t)dt=∫ ₀ ^(t) ^(r) R(t)dt=C   (1)

The length of the entire adsorption-regeneration cycle, T, is given by

T=t _(a) +t _(r) +t _(s)   (2)

where t_(s) is the optional switchover or pause time between adsorptionphase and regeneration phase; for example, time allowed for theadsorbent to cool down or warm up as needed.

Since the amount of CO₂ removed from the indoor air in each such cycleis C, the overall system productivity, p—defined as the average amountof CO₂ removed per unit time—is simply

p=C/T   (3)

But the value of p depends not only on the adsorbent and the environmentin which it operates but also on our choice of t_(a) and t_(r).

According to an embodiment, the optimal choice of t_(r), for anyparticular set of conditions in terms of temperature, flow rates and CO₂concentrations, may be approximately identified. In plugging equations(2) and (1) into (3) the following is received:

$\begin{matrix}{p = {{C/T} = \frac{\int_{O}^{t_{r}}{{R(t)}{dt}}}{t_{a} + t_{r\;} + t_{s}}}} & (4)\end{matrix}$

Through basic calculus, the maximum value for p is obtained by takingits derivative with respect to t_(r) and equating it to zero, namely

$\begin{matrix}{\frac{dp}{{dt}_{r}} = 0} & (5)\end{matrix}$

Which can be expanded using basic derivative rules that state generally

$\begin{matrix}{{\frac{d}{dx}\left( \frac{f}{g} \right)} = \frac{\left( {{\begin{matrix}{df} \\{dx}\end{matrix}g} - {\begin{matrix}{d\; g} \\{dx}\end{matrix}f}} \right)}{g^{2}}} & (6)\end{matrix}$

So equation (5) requires

$\begin{matrix}{{\frac{d}{{dt}_{r}}\left( \frac{C}{T} \right)} = {\frac{\left( {{\frac{dC}{{dt}_{r}}T} - {\frac{dT}{{dt}_{r}}C}} \right)}{T^{2}} = 0}} & (7)\end{matrix}$

Which implies that

$\begin{matrix}{{{\frac{dC}{{dt}_{r}}T} - {\frac{dT}{{dt}_{r}}C}} = 0} & (8)\end{matrix}$

Or in other words

$\begin{matrix}{{\frac{dC}{{dt}_{r}}/C} = {\frac{dT}{{dt}_{r}}/T}} & (9)\end{matrix}$

This condition, although not an immediately solvable equation, is animportant insight for the optimal design of indoor air adsorbentscrubbers, such as for single adsorbents or for more than one adsorbentdesigns. It can be further reduced to practice using the fact that, bydefinition,

$\begin{matrix}{\frac{dC}{{dt}_{r}} = {R\left( t_{r} \right)}} & (10)\end{matrix}$

And assuming t, is independent of t_(r),

$\begin{matrix}{\frac{dT}{{dt}_{r}} = \left( {1 + \frac{{dt}_{a}}{{dt}_{r}}} \right)} & (11)\end{matrix}$

The following condition for t_(r) is received

$\begin{matrix}{{R\left( t_{r} \right)} = {{\left( {1 + \frac{{dt}_{a}}{{dt}_{r}}} \right) \times p} = {\beta \; p}}} & (12)\end{matrix}$

Where a new parameter, β, is introduced and may be simply defined as

$\begin{matrix}{\beta \equiv {1 + \frac{{dt}_{a}}{{dt}_{r}}}} & (13)\end{matrix}$

Admittedly equation (12) is still not an explicit closed form expressionthat allows calculation of t_(r), but it is a useful design condition,and it does immediately suggest a lower bound, since β is always greaterthan 1. That means that at a minimum, it may be economically preferableto stop regeneration before the instantaneous rate R(t) drops below p,namely the following condition should be maintained

R(t _(r))≥p   (14)

It is a more reasonable estimate that

$\begin{matrix}{\left( \frac{{dt}_{s}}{{dt}_{r}} \right)\text{∼}1} & (15)\end{matrix}$

So it can be better approximated that β≈2, thus having an even earlierthreshold for stopping regeneration at

R(t_(r))˜2p   (16)

Technically it remains an open equation because the value of p is notfixed, but it can be solved by iterations. This is a useful andpractical guideline especially since the value of p varies relativelyslowly with changes in t_(r) so a few iterations will quickly convergeon a very good approximation.

In some embodiments, empirically a more precise value for β can bederived, which would help refine formula (16), this may be performed bymeasuring the rate of adsorption towards the end of the cycle andcomparing it to the rate of desorption. Two extremes are worthelaborating further.

In the case of classical “breakthrough”, the adsorption ratedramatically falls at the end of the cycle which means dt_(a)>>dt_(r)and β>>1, which translates into such a high threshold for R thatregeneration may be stopped. In other words there may be no point orbenefit in extending the regeneration phase if doing so does only causeslingering in adsorption mode post-breakthrough.

When there is only a very gradual decline in A(t) towards the end of thecycle, the opposite holds, namely dt_(a)<dt_(r) and β≈1, which meansequation (14) is a good design criterion for timing the duration of theregeneration step.

It is noted that the principles described in this disclosure apply to awide variety of scrubbing applications and CO₂ or other pollutantsremoval applications using adsorbents in an adsorption-release cycle,and are not limited to indoor air applications.

As described above, in some embodiments, the regeneration phase may beterminated upon the regeneration rate R(t_(r)) of the adsorbent beingbetween about equal to and a predetermined amount less than theproductivity p of the complete regeneration phase, where productivityp=C/T, and C equals an amount of the pollutant and/or first gas adsorbedby the adsorbent from the stream of gases during one cycle and T is theduration of one cycle period. This predetermined amount less than theproductivity may be any suitable amount. In a non-limiting example, thepredetermined amount may be in the range of 20-98% of the productivity pof the complete regeneration phase.

In some embodiments, the regeneration phase is terminated upon aregeneration rate R(t_(r)) being between about equal to and about twicea productivity p of the complete regeneration phase, where productivityp=C/T, and C equals an amount of the pollutant and/or first gas adsorbedby the adsorbent from the stream of gases during one cycle and T is theduration of one cycle period.

In accordance with some embodiments there is described a method forremoving a gas component including at least one adsorbate (which mayalso be referred to herein as a pollutant(s) and/or a particular gas(s))from a stream of mixed gases, the method may comprise one or more of:using an adsorbent material in a repeated cyclical fashion, with atleast two distinct phases in each cycle, one being an adsorption phasewhere the adsorbate is partially removed from the streaming gas mixtureonto the adsorbent, and one being a regeneration phase where theadsorbate is released from the adsorbent and carried away. The durationof the regeneration phase may be substantially shorter than a completeregeneration phase, the complete regeneration phase being the time torelease substantially all of the adsorbate that can be released underthe temperature and flow conditions of the system.

In accordance with some embodiments at least an additional 10% of theadsorbate could be released if the regeneration phase were extended by100%. Alternatively, at least an additional 5% of the adsorbate could bereleased if the regeneration phase were extended by 100%.

The example set forth herein is meant to exemplify various aspects ofthe disclosure and is not intended to limit in any way.

EXAMPLE

Reference is made to FIG. 4, which is a graph showing a method forcalculating the optimal adsorption-regeneration cycle and in accordancewith the formulas described hereinabove. As seen in FIG. 4 the values ofthe following parameters are substantially:

t_(a)=53 min

t_(s)=5 min

t_(r)=34 min

Thus, T is the sum of t_(a+), t₂+t_(r)=92 min

C=70 grams

Therefore p=C/T=70/92=0.76 [grams per minutes]

Thus, the regeneration may be stopped where R(t_(r)) according toformula (14) is equal or larger than 0.76 (grams per minutes) oraccording to formula (16) where R(t_(r)) is substantially equal to 1.52(grams per minutes).

In accordance with some embodiments prior to streaming the regenerationair flow in the reverse direction to the incoming air, as described inreference to FIGS. 1A-3, or in the same direction, the following may bedetermined: the amount of the pollutant in the scrubbed air flow and/orthe ability of the adsorbent to capture an additional amount of thepollutant over and above a predetermined amount, and when the amount ofthe pollutant is greater than a predetermined amount, and/or theadsorbent has captured the predetermined amount of the pollutant,streaming of the regeneration air flow over and/or through the adsorbentis performed.

The amount of the pollutant in the scrubbed air flow and/or the abilityof the adsorbent to capture an additional amount of the at least onepollutant may be determined in any suitable manner, such as by acomputer including a processor and a non-transitory machine-readablemedium (for example).

This predetermined amount of the pollutant may be any suitable amount.In a non-limiting example, the predetermined amount may be an amount ofthe pollutant that substantially saturates the adsorbent. In anon-limiting example, the predetermined amount may be less than theamount of the pollutant that substantially saturates the adsorbent.

In accordance with some embodiments prior to streaming the regenerationair flow in the reverse direction to the incoming air, as described inreference to FIGS. 1A-3, or in the same direction, the following may bedetermined: a level of an adsorption efficiency, where the adsorptionefficiency at any point in time during the one cycle has a value of1−C_(in)/C_(out). C_(in) is the concentration of the pollutant in theincoming air flow and C_(out) is the concentration of the pollutant inthe outgoing air flow. When the adsorption efficiency value is less thanan initial adsorption efficiency value, streaming of the regenerationair flow over and/or through the adsorbent is performed. The initialadsorption efficiency value is the adsorption efficiency value at thebeginning of the adsorption phase.

The adsorption efficiency value and the initial adsorption efficiencyvalue may be determined in any suitable manner, such as by a computerincluding a processor and a non-transitory machine-readable medium (forexample).

In some embodiments, where the adsorption efficiency value is less thanthe initial adsorption efficiency value, a regeneration air flow isstreamed through the air treatment assembly 102 and over and/or throughthe adsorbent in a second direction opposite to the first direction ofthe incoming air, such that the regeneration air flow regenerates atleast some of the adsorbent and purges at least some of the pollutantsfrom the adsorbent.

In some embodiments, streaming of the regeneration air flow over and/orthrough the adsorbent is performed where the adsorption efficiency valueis at least about 20% less than the initial adsorption efficiency value.In some embodiments, streaming of the regeneration air flow over and/orthrough the adsorbent is performed where the adsorption efficiency valueis at least about 30% less than the initial adsorption efficiency value.In some embodiments, streaming of the regeneration air flow over and/orthrough the adsorbent is performed where the adsorption efficiency valueis at least about 50% less than the initial adsorption efficiency value.In some embodiments, streaming of the regeneration air flow over and/orthrough the adsorbent is performed where the adsorption efficiency valueis at least about 80% less than the initial adsorption efficiency value.

In is noted that the air treatment assembly 102 described above inreference to FIGS. 1A-4, may be configured to treat any stream of gas,such as air from the enclosed environment 110, flue gases, or nitrogenwith elevated levels of carbon dioxide, organic contaminants relative tosubstantially unpolluted air, or outside air.

Various implementations of some of embodiments disclosed, in particularat least some of the processes discussed (or portions thereof), may berealized in digital electronic circuitry, integrated circuitry,specially designed ASICs (application specific integrated circuits),computer hardware, firmware, software, and/or combinations thereof.These various implementations may include implementation in one or morecomputer programs that are executable and/or interpretable on aprogrammable system including at least one programmable processor, whichmay be special or general purpose, coupled to receive data andinstructions from, and to transmit data and instructions to, a storagesystem, at least one input device, and at least one output device.

Such computer programs (also known as programs, software, softwareapplications or code) include machine instructions/code for aprogrammable processor, for example, and may be implemented in ahigh-level procedural and/or object-oriented programming language,and/or in assembly/machine language. As used herein, the term“machine-readable medium” refers to any computer program product,apparatus and/or device (e.g., non-transitory mediums including, forexample, magnetic discs, optical disks, flash memory, Programmable LogicDevices (PLDs)) used to provide machine instructions and/or data to aprogrammable processor, including a machine-readable medium thatreceives machine instructions as a machine-readable signal. The term“machine-readable signal” refers to any signal used to provide machineinstructions and/or data to a programmable processor.

To provide for interaction with a user, the subject matter describedherein may be implemented on a computer having a display device (e.g., aCRT (cathode ray tube) or LCD (liquid crystal display) monitor and thelike) for displaying information to the user and a keyboard and/or apointing device (e.g., a mouse or a trackball, touchscreen) by which theuser may provide input to the computer. For example, this program can bestored, executed and operated by the dispensing unit, remote control,PC, laptop, smart-phone, media player or personal data assistant(“PDA”). Other kinds of devices may be used to provide for interactionwith a user as well. For example, feedback provided to the user may beany form of sensory feedback (e.g., visual feedback, auditory feedback,or tactile feedback), and input from the user may be received in anyform, including acoustic, speech, or tactile input.

Certain embodiments of the subject matter described herein may beimplemented in a computing system and/or devices that includes aback-end component (e.g., as a data server), or that includes amiddleware component (e.g., an application server), or that includes afront-end component (e.g., a client computer having a graphical userinterface or a Web browser through which a user may interact with animplementation of the subject matter described herein), or anycombination of such back-end, middleware, or front-end components. Thecomponents of the system may be interconnected by any form or medium ofdigital data communication (e.g., a communication network). Examples ofcommunication networks include a local area network (“LAN”), a wide areanetwork (“WAN”), and the Internet.

The computing system according to some such embodiments described abovemay include clients and servers. A client and server are generallyremote from each other and typically interact through a communicationnetwork. The relationship of client and server arises by virtue ofcomputer programs running on the respective computers and having aclient-server relationship to each other.

Any and all references to publications or other documents, including butnot limited to, patents, patent applications, articles, webpages, books,etc., presented anywhere in the present application, are hereinincorporated by reference in their entirety.

Example embodiments of the devices, systems and methods have beendescribed herein. As may be noted elsewhere, these embodiments have beendescribed for illustrative purposes only and are not limiting. Otherembodiments are possible and are covered by the disclosure, which willbe apparent from the teachings contained herein. Thus, the breadth andscope of the disclosure should not be limited by any of theabove-described embodiments but should be defined only in accordancewith claims supported by the present disclosure and their equivalents.Moreover, embodiments of the subject disclosure may include methods,systems and devices which may further include any and allelements/features from any other disclosed methods, systems, anddevices, including any and all features corresponding to translocationcontrol. In other words, features from one and/or another disclosedembodiment may be interchangeable with features from other disclosedembodiments, which, in turn, correspond to yet other embodiments.Furthermore, one or more features/elements of disclosed embodiments maybe removed and still result in patentable subject matter (and thus,resulting in yet more embodiments of the subject disclosure).

What is claimed is:
 1. A method for controlling a scrubber containing an adsorbent, the scrubber configured to cycle between scrubbing at least one pollutant and/or first gas from a stream of gases with the at least one pollutant and/or first gas being adsorbed onto the adsorbent, and regenerating at least some of the adsorbent and thereby purging at least some of the at least one pollutant and/or first gas from the adsorbent via a regeneration gas flow, the method comprising: flowing a stream of gases through the scrubber, the scrubber comprising the adsorbent; adsorbing at least some of the one pollutant and/or first gas from the stream of gases onto the adsorbent during an adsorption phase over a first time period; purging a portion of the at least one pollutant and/or first gas from the adsorbent during a regeneration phase over a second time period with a regeneration gas flow, and cycling between the adsorption phase and the regeneration phase, wherein one cycle comprises at least an adsorption phase followed by a regeneration phase, one cycle period comprises the total time elapsed during one cycle, the at least one pollutant and/or first gas purged from the adsorbent is carried away by the regeneration gas flow, and a complete regeneration phase comprises a time period for removing substantially all of the pollutant and/or first gas from the adsorbent during the regeneration phase, and a complete adsorption phase comprises a time period for substantially saturating all the adsorbent during the adsorption; and limiting at least one of: the duration of the first time period to a period of time which is less than the complete adsorption phase, and the duration of the second time period to a period of time which is less than the complete regeneration phase.
 2. The method of claim 1, wherein the first time period comprises about 95% of a complete adsorption phase.
 3. The method of claim 1, wherein the first time period is about 90% of a complete adsorption phase.
 4. The method of claim 1, wherein the first time period is about 80% of a complete adsorption phase.
 5. The method of claim 1, wherein the first time period is about 50% of a complete adsorption phase.
 6. The method of claim 1, wherein the first time period is about 20% of a complete adsorption phase.
 7. The method of claim 1, wherein the first time period comprises about 20% to about 95% of a complete adsorption phase.
 8. The method of claim 1, wherein the second time period comprises about 95% of a complete regeneration phase.
 9. The method of claim 1, wherein the second time period is about 90% of a complete regeneration phase.
 10. The method of claim 1, wherein the second time period is about 80% of a complete regeneration phase.
 11. The method of claim 1, wherein the second time period is about 50% of a complete regeneration phase.
 12. The method of claim 1, wherein the second time period is about 20% of a complete regeneration phase.
 13. The method of claim 1, wherein the second time period comprises about 20% to about 95% of a complete regeneration phase.
 14. The method of claim 1, wherein: the regeneration phase is terminated upon a regeneration rate R(t_(r)) of the adsorbent being between about equal to and a predetermined amount less than a productivity p of the complete regeneration phase, wherein productivity p=C/T, and C equals an amount of the pollutant and/or first gas adsorbed by the adsorbent from the stream of gases during one cycle and T is the duration of one cycle period.
 15. The method of claim 1, wherein: the regeneration phase is terminated upon a regeneration rate R(t_(r)) being between about equal to and about twice a productivity p of the complete regeneration phase, wherein productivity p=C/T, and C equals an amount of the pollutant and/or first gas adsorbed by the adsorbent from the stream of gases during one cycle and T is the duration of one cycle period.
 16. The method of claim 1, wherein the pollutant and/or first gas is selected from the group consisting of: carbon dioxide, volatile organic compounds, sulfur oxides, radon, nitrous oxides and carbon monoxide.
 17. The method of claim 1, wherein the adsorbent comprises at least one of : an amine supported by a solid, activated carbon, clay, carbon fibers, silica, alumina, zeolites, molecular sieves, titanium oxide, polymer, porous polymers, polymer fibers and metal organic frameworks.
 18. The method of claim 17, wherein the supporting solid is at least one of silica, carbon, clay or metal oxide.
 19. The method of claim 1, wherein the adsorbent comprises granular solids or pelleted shaped solids.
 20. The method of claim 1, wherein the stream of gases comprises air from an enclosed environment, outdoor air, flue gases, or nitrogen with elevated levels of carbon dioxide or organic contaminants, relative to substantially unpolluted air.
 21. The method of claim 1 wherein the one cycle may further comprise at least one of: (i) a first switchover phase prior to the regeneration phase, and (ii) a second switchover phase following the regeneration phase.
 22. The method of claim 21, wherein the second switchover phase comprises a period of time to bring the adsorbent to a temperature to adsorb the at least one pollutant and/or first gas during the adsorption phase.
 23. The method of claim 21, wherein the first switchover phase comprises a period of time to bring the adsorbent to a temperature to release the at least one pollutant and/or first gas from the adsorbent during the regeneration phase.
 24. The method of claim 1, wherein prior to streaming the regeneration gas flow the method further includes determining a level of an adsorption efficiency, wherein the adsorption efficiency at any point in time during the one cycle has a value of 1−C_(in)/C_(out), wherein C_(in) is the concentration of the pollutant in the incoming air flow and C_(out) is the concentration of the pollutant in an outgoing air flow, and wherein an initial adsorption efficiency value is the adsorption efficiency value at the beginning of the adsorption phase, wherein the adsorption efficiency value is less than the initial adsorption efficiency value, streaming of the regeneration gas flow over and/or through the adsorbent is performed.
 25. A system for controlling a scrubber, the system comprising: a scrubber containing an adsorbent, the scrubber configured to cycle between scrubbing at least one pollutant and/or first gas from a stream of gases with the at least one pollutant and/or first gas being adsorbed onto the adsorbent, and purging the at least one pollutant and/or first gas from the adsorbent via a regeneration gas flow; means for flowing the stream of gases through the scrubber and over and/or through the adsorbent, wherein the adsorbent adsorbs at least one pollutant and/or first gas from the stream of gases during an adsorption phase over a first time period; means for flowing the regeneration gas flow over the adsorbent for purging a portion of the pollutant and/or first gas from the adsorbent during a regeneration phase over a second time period with a regeneration gas flow, and means for cycling between the adsorption phase and the regeneration phase, wherein one cycle comprises one adsorption phase followed by one regeneration phase, one cycle period comprises the total time elapsed during one cycle; the pollutant and/or first gas purged from the adsorbent is carried away by the regeneration gas flow, a complete regeneration phase comprises a time period for removing substantially all of the pollutant and/or first gas from the adsorbent during the regeneration phase, a complete adsorption phase comprises a time period for substantially saturating all the adsorbent during the adsorption, and the duration of at least one of the following is limited: the duration of the first time period to a period of time which is less than the complete adsorption phase, and the duration of the second time period to a period of time which is less than the complete regeneration phase.
 26. The system of claim 25, wherein the means for cycling comprises a processor and a non-transitory machine-readable medium storing instructions having computer instructions operating thereon for controlling cycling between the adsorption and regeneration phases.
 27. A computer implemented method for controlling a scrubber containing an adsorbent, the scrubber configured to cycle between scrubbing at least one pollutant and/or first gas from a stream of gases with the at least one pollutant and/or first gas being adsorbed onto the adsorbent, and purging the at least one pollutant and/or first gas from the adsorbent via a purging gas flow, the method comprising: flowing a stream of gases through the scrubber, the scrubber comprising an adsorbent; adsorbing at least one pollutant and/or first gas from the stream of gases onto the adsorbent during an adsorption phase over a first time period, purging a portion of the at least one pollutant and/or first gas from the adsorbent during a regeneration phase over a second time period with a regeneration gas flow, and cycling between the adsorption phase and the regeneration phase, wherein one cycle comprises one adsorption phase followed by one regeneration phase, one cycle period comprises the total time elapsed during one cycle; the at least one pollutant and/or first gas purged from the adsorbent is carried away by the regeneration gas flow, and a complete regeneration phase comprises a time period for removing substantially all of the pollutant and/or first gas from the adsorbent during the regeneration phase, a complete adsorption phase comprises a time period for substantially saturating all the adsorbent during the adsorption; and limiting at least one of: the duration of the first time period to a period of time which is less than the complete adsorption phase, and the duration of the second time period to a period of time which is less than the complete regeneration phase, wherein at least one of the above is performed by at least one processor.
 28. A system for controlling a scrubber containing an adsorbent, the scrubber configured to cycle between scrubbing at least one pollutant and/or first gas from a stream of gases with the at least one pollutant and/or first gas being adsorbed onto the adsorbent, and purging the at least one pollutant and/or first gas from the adsorbent via a regeneration gas flow, the system comprising at least one processor and a non-transitory machine-readable medium storing instructions that, when executed by the at least one processor, perform the method comprising: flowing a stream of gases over and/or through the adsorbent, wherein the adsorbent adsorbs at least some of the at least one pollutant and/or first gas from the stream of gases during an adsorption phase over a first time period; purging a portion of the at least one pollutant and/or first gas from the adsorbent during a regeneration phase over a second time period with a regeneration gas flow, and cycling between the adsorption phase and the regeneration phase, wherein one cycle comprises one adsorption phase followed by one regeneration phase, one cycle period comprises the total time elapsed during one cycle, the at least one pollutant and/or first gas being purged from the adsorbent is carried away by the regeneration gas flow, and a complete regeneration phase comprises a time period for removing substantially all of the at least one pollutant and/or first gas from the adsorbent during the regeneration phase, a complete adsorption phase comprises a time period for substantially saturating all the adsorbent during the adsorption, and limiting at least one of: the duration of the first time period to a period of time which is less than the complete adsorption phase, and the duration of the second time period to a period of time which is less than the complete regeneration phase.
 29. A method for reducing the level of at least one pollutant contained in indoor air from a human-occupied, enclosed environment, the method comprising: providing an air treatment assembly including at least one type of adsorbent, the adsorbent configured for capturing at least one pollutant entrained in an indoor air flow from the enclosed environment and regenerating upon exposure to a regenerating gas flow; streaming the indoor air flow over and/or through the adsorbent in a first direction such that the adsorbent captures at least some of the at least one pollutant from the indoor air flow, wherein after being flowed over and/or through the adsorbent, the air flow comprises a scrubbed air flow; and streaming the regeneration gas flow over and/or through the adsorbent in a second direction opposite to the first direction, such that the regeneration gas flow regenerates at least some of the adsorbent and purges at least some of the at least one pollutant from the adsorbent.
 30. The method of claim 29 where there are at least two adsorbents such that the streaming indoor air flows through a first adsorbent and subsequently through a second adsorbent, and that as a result of the reversal of the flow direction during regeneration, substances purged from the first adsorbent do not flow across the second adsorbent.
 31. The method of claim 29 where pollutants are released from the adsorbent during regeneration and may accumulate in the air treatment assembly or air conduits attached to it, and as a result of the reversal of the flow direction during regeneration, the released pollutants are substantially prevented from accumulating downstream from the adsorbent and accumulate substantially in sections of the air treatment assembly that are upstream from the adsorbent, the air treatment assembly comprising an inlet for indoor air flowing through the adsorbent; and upstream the adsorbent being in greater proximity to the inlet than downstream the adsorbent.
 32. The method of claim 29, wherein the pollutant and/or first gas is selected from the group consisting of: carbon dioxide, volatile organic compounds, sulfur oxides, radon, nitrous oxides and carbon monoxide.
 33. The method of claim 29, wherein the adsorbent comprises at least one of an amine supported by a solid, activated carbon, clay, carbon fibers, silica, alumina, zeolites, molecular sieves, titanium oxide, polymer, porous polymers, polymer fibers and metal organic framework.
 34. The method of claim 33, wherein the supporting solid is at least one of silica, carbon, clay or metal oxide.
 35. The method of claim 29, wherein the adsorbent comprises granular solids or pelleted shaped solids.
 36. A computer implemented method for reducing the level of at least one pollutant contained in indoor air from an enclosed, human-occupied environment, the method comprising: streaming an indoor air flow over and/or through an adsorbent provided within an air treatment assembly in a first direction, the indoor air flow containing at least one pollutant from inside the enclosed environment, such that the adsorbent captures at least some of the at least one pollutant from the indoor air, wherein after being flowed over and/or through the adsorbent, the air flow comprises a scrubbed air flow; determining a level of an adsorption efficiency, wherein the adsorption efficiency at any point in time during the one cycle has a value of 1−C_(in)/C_(out), wherein C_(in) is the concentration of the pollutant in the incoming air flow and C_(out) is the concentration of the pollutant in an outgoing air flow, and wherein an initial adsorption efficiency value is the adsorption efficiency value at the beginning of the adsorption phase, wherein the adsorption efficiency value is less than the initial adsorption efficiency value, and streaming a regeneration air flow through the air treatment assembly and over and/or through the adsorbent in a second direction opposite to the first direction, such that the regeneration air flow regenerates at least some of the adsorbent and purges at least some of the at least one pollutant from the adsorbent, wherein at least one of the above is performed by a processor.
 37. A system for reducing the level of at least one pollutant contained in indoor air from an enclosed, human-occupied environment, the method comprising: an air treatment assembly including an adsorbent, the adsorbent configured for capturing at least one pollutant entrained in an indoor air flow and regenerating upon exposure to a regenerating gas flow; and streaming means for: streaming the indoor air flow over and/or through the adsorbent in a first direction, such that the adsorbent captures at least some of the at least one pollutant from the indoor air flow, and streaming the regeneration air flow over and/or through the adsorbent in a second direction opposite to the first direction, such that the regeneration gas flow regenerates at least some of the adsorbent and purges at least some of the at least one pollutant from the adsorbent.
 38. A system for reducing the level of at least one pollutant contained in indoor air from an enclosed, human-occupied environment, the system comprising: an air treatment assembly including an adsorbent, the adsorbent configured for capturing at least one pollutant entrained in an indoor air flow and regenerating upon exposure to a regenerating gas flow; streaming means for streaming the indoor air flow over and/or through the adsorbent in a first direction, and/or for streaming the regeneration gas flow over and/or through the adsorbent in a second direction opposite to the first direction; at least one processor; a non-transitory machine-readable medium storing instructions that, when executed by the at least one processor, perform the method comprising: streaming the indoor air over and/or through the adsorbent in the first direction such that the adsorbent captures at least some of the at least one pollutant from the indoor air; and determining a level of an adsorption efficiency, wherein the adsorption efficiency at any point in time during the one cycle has a value of 1−C_(in)/C_(out), wherein C_(in) is the concentration of the pollutant in the incoming air flow and C_(out) is the concentration of the pollutant in an outgoing air flow, and wherein an initial adsorption efficiency value is the adsorption efficiency value at the beginning of the adsorption phase, wherein the adsorption efficiency value is less than the initial adsorption efficiency value, streaming of the regeneration gas flow over and/or through the adsorbent is performed.
 39. A method for reducing the level of at least one pollutant contained in indoor air from an enclosed, human-occupied environment, the method comprising: providing an air treatment assembly including an adsorbent, the adsorbent configured for capturing at least one pollutant entrained in an indoor air flow from the enclosed environment and regenerating upon exposure to a regenerating gas flow; streaming the indoor air flow over and/or through the adsorbent in a first direction such that the adsorbent captures at least some of the at least one pollutant from the indoor air flow, wherein the streaming of the indoor air flow over and/or through the adsorbent comprises an adsorption phase; and streaming the regeneration gas flow over and/or through the adsorbent in a second direction opposite to the first direction, such that the regeneration air flow regenerates at least some of the adsorbent and purges at least some of the at least one pollutant from the adsorbent, wherein the streaming of the regeneration gas flow over and/or through the adsorbent comprises a regeneration phase, cycling between the adsorption phase and the regeneration phase, wherein one cycle comprises an adsorption phase followed by a regeneration phase, one cycle period comprises the total time elapsed during one cycle; the at least one pollutant purged from the adsorbent is carried away by the regeneration gas flow, and a complete regeneration phase comprises a time period for removing substantially all of the at least one pollutant from the adsorbent during the regeneration phase, and and a complete adsorption phase comprises a time period for substantially saturating all the adsorbent during the adsorption; and limiting at least one of: the duration of the first time period to a period of time which is less than the complete adsorption phase, and the duration of the second time period to a period of time which is less than the complete regeneration phase.
 40. The method of claim 39, wherein prior to steaming the regeneration gas flow the method further includes determining a level of an adsorption efficiency, wherein the adsorption efficiency at any point in time during the one cycle has a value of 1−C_(in)/C_(out), wherein C_(in) is the concentration of the pollutant in the incoming air flow and C_(out), is the concentration of the pollutant in an outgoing air flow, and wherein an initial adsorption efficiency value is the adsorption efficiency value at the beginning of the adsorption phase, wherein the adsorption efficiency value is less than the initial adsorption efficiency value, streaming of the regeneration gas flow over and/or through the adsorbent is performed.
 41. The method of claim 40 wherein the adsorption efficiency value is at least about 20% less than the initial adsorption efficiency value.
 42. The method of claim 40 wherein the adsorption efficiency value is at least about 30% less than the initial adsorption efficiency value.
 43. The method of claim 40 wherein the adsorption efficiency value is at least about 50% less than the initial adsorption efficiency value.
 44. The method of claim 40 wherein the adsorption efficiency value is at least about 80% less than the initial adsorption efficiency value. 